This invention relates in general to gear hinges and more particularly to knuckle-type bearings for gear hinges and to gear hinges having such bearings.
A door attached to a door frame with traditional pin-type hinges has its weight concentrated at the few relatively small areas at which the hinges are located. Due to the concentration of weight at these areas, it is not uncommon to find the screws which secure the hinge leaves pulled free from the door or hinge jamb, or to find the jamb bent, or to find the hinge leaves themselves bent, particularly when the door is subjected to abuse. A continuous gear hinge, on the other hand, usually extends the entire length of a hinge jamb and door and thus distributes the weight of the door over a much larger area. For this reason gear hinges are often installed on doors which see heavy use, such as those found in public buildings, or on doors which encounter abuse, such as those at schools.
A gear hinge basically consists of two leaves having meshing gear segments, a clamp for holding the gear segments together so that the door leaf can rotate relative to the jamb leaf while the gear segments remain meshed, and a bearing block for preventing the door leaf from shifting longitudinally relative to the jamb leaf. A gear hinge for a typical door will have several bearing blocks fitted to cutouts formed in its gear segments, and these blocks, which are usually molded from plastic, carry essentially the entire weight of the door. As the hinge opens and closes, the metal edges of the cutouts in the gear segments slide over the end faces of the plastic blocks, and the blocks wear. In time they must be replaced, and this usually requires removing the hinge from the door jamb to obtain enough clearance to slide the clamp free of the gear segments. U.S. Pat. No. 3,402,422 shows a gear hinge having a traditional bearing.
The present invention resides in a gear hinge and a bearing for such a hinge. The bearing has blocks provided with interlocking knuckles, the side faces of which serve as low friction surfaces through which thrust or longitudinal loading on the hinge is transmitted.